"I used to get the more distant FMs late at night, for some reason, of which I am not clear."

The sun offers a tremendous amount of interference on a broadband basis. When the sun is gone, signals propagate better. Groundwave at the radio horizon (and slightly beyond - don't ask for an explanation of the "slightly beyond" part) become more receivable because there is less solar interference (as long as you aren't close to co channel or first adjacent signals). If it's cloudy you can also experience E-skip skywave at FM band frequencies. Clearly not like AM channels, but the signals do bounce around when the atmospheric conditions are "thick."

I remember picking up 106.7 when it was on Mt. Scott down in southern Oregon on I-5 between Grants Pass and Roseburg as I was traveling north every time I would hit a hill peak and start coming down the north side.

Before the KGON tower when most of the FM stations were on KXL, You could hear most of those station at least to Wolf Creek area north of Grants Pass. Not anymore. I suppose Beam tilt antennas might have something to do with that.

More likely the effect of the increased number of FM stations on the air rather than beam tilt. For example, from Hillsboro, KSOR (90.1) Ashland was a fairly regular catch before KAJC (90.1) Salem hit the air. Most Vancouver BC stations that I could receive in the 80s-90s are covered now by closer stations/translators/HD carriers. The band is filling up and noise levels are increasing.

Thank you, Andy. That was in the 1970s, with a giant Radio Shack FM antenna with rotor on the roof, attached to the living room home entertainment center(remember those?). One of the stations that came in all the time was KOMS at 30KW, before they raised power. Needless to say, there wasn't much selectivity.

More likely the effect of the increased number of FM stations on the air rather than beam tilt.

Yes, that's true, but certain frequencies such as 95.5 and 97.1 don't have that problem, yet they now don't reach Wolf Creek (at least not the recent times I've been through there). I suppose that the new shorter antennas might also have something to do with it as well.

"Yes, that's true, but certain frequencies such as 95.5 and 97.1 don't have that problem, yet they now don't reach Wolf Creek (at least not the recent times I've been through there)."

It's subtle, but every station added to the band raises the "noise floor" and degrades DX reception for all stations.
It is also likely that your long distance reception was obtained during favorable tropo conditions. When I mentioned reception of KSOR (Ashland) and Vancouver BC stations above, reception was *not* constant, but the stations could be heard from Hillsboro on "good days".

"I suppose that the new shorter antennas might also have something to do with it as well."

What I have been using so far is an early 1990s vintage Technics tuner modified with 180 kHz IF filters. With this tuner, the noise floor goes up considerably when I point the antenna east, due to overload. HD sidebands are also making a mess of the band (I can even hear these on my car radio at various spots on the dial).